Some questions regarding the electrical desalination of crude oil

1. Generally, oil contains water after it is extracted, and this water contains substances such as NaCl, CaCl2, and MgCl2; meanwhile, some salts exist in the form of naphthenates. 2. Generally, higher water content implies higher salt content as well. Of course, if the electrodialyzed water is not properly mixed with the crude oil or if the demulsification effect is poor, even when the crude oil contains less water after desalination, there will still be a significant amount of salt present. 3. The factors affecting the demulsification effect include the temperature of crude oil entering the electrodesalination unit, mixing intensity, the effectiveness of the demulsifier, and the amount of water injected

1. There are many salts present in crude oil, but sodium chloride, calcium chloride, and magnesium chloride account for the majority； 2. A low water content in crude oil does not necessarily mean a low salt content; the level of water content is related to extraction methods as well as the degree of oil-water emulsification ； 3. Demulsifier efficiency: a is related to the compatibility of the demulsifier with crude oil; b is related to the mixing intensity before electrodialysis

The two people above have already explained it in some detail; I’ll add a couple more points. In addition to the inorganic salts mentioned above, crude oil also contains a certain amount of organic salts. There is no corresponding relationship between the salts in crude oil and its water content. Don’t you see that in electrodesalination units, 4%-8% of water is also added? This is to dissolve the inorganic salts in the crude oil in water, and through the action of an electric field, these salts are transferred from the oil phase to the water phase. Due to the presence of organic salts in the oil, the salt content after electrodialysis sometimes fails to meet the 3 ppm requirement, as organic salts are insoluble in the aqueous phase. Furthermore, the demulsification effect is mainly related to the operation conditions of the electrodesalination unit, the choice of demulsifier, and the properties of the crude oil. This topic is too broad; only a general discussion is possible. As for how to achieve an excellent demulsification effect, it depends on each manufacturer to explore and optimize the configuration of the equipment, additives, and the properties of the crude oil on their own.

Crude oil generally contains both inorganic and organic salts; the inorganic salts mainly include sodium chloride, calcium chloride, etc., while the organic salts are primarily naphthenates. Generally, when crude oil contains a high level of water, it also contains more salt; however, there is no linear relationship between these two factors. Although crude oil after electrodialysis has less water content, if the injected water does not mix properly with the crude oil, the desalination effect is poor and the salt content cannot meet the required standards. There are many factors that affect the demulsification effect of demulsifiers. The main ones include: 1. Electric field strength – in principle, the stronger the electric field strength, the better the desalination effect, but it also increases the energy consumption of the equipment ； 2. Desalination temperature: A higher temperature helps to reduce the viscosity of crude oil and decrease the resistance to the movement of water droplets. However, this temperature depends on the heat exchange network; generally, when the crude oil is less viscous, it is possible to use a lower temperature. 3. Currently, oil-soluble demulsifiers are widely used, as this helps to improve mixing with crude oil. 4. Water injection volume: Water injection in electrodesalination is primarily used to remove salts from crude oil, and the amount of water injected also affects the desalination efficiency; it is generally kept at around 5%. 5. Pressure in the desalination tank: The pressure is controlled primarily to prevent the vaporization of light components in the crude oil, so as not to affect the sedimentation of water. 6. Mixing pressure difference: A higher mixing pressure difference can improve the mixing of water injection, demulsifier, and crude oil; however, an excessively high pressure difference will cause more severe emulsification of oil and water, preventing the demulsifier from functioning effectively. 7. The dosage of the demulsifier: There is an optimal amount of demulsifier to be used, and this needs to be determined through practical experimentation.

1. The salts in crude oil are mainly divided into inorganic and organic salts. Inorganic salts should exist in water in ionic form, while organic salts should exist in crude oil as molecular compounds ； 2. A low or trace amount of water in crude oil does not necessarily mean that the salt content is low; this is probably why dehydration occurs rather than direct evaporation of water ； 3. The demulsification effect should be related to the properties of the crude oil itself, such as its viscosity, and it affects the desalination process, thereby having a direct impact on the efficiency of desalination.